1. Field of the Invention
This invention relates, generally, to devices that help clinicians practice finding and accessing veins. More particularly, it relates to a device having utility with near-infrared vein imagers.
2. Description of the Prior Art
Gaining access to a vein with a hypodermic needle requires no visual or mechanical aid if the vein is near the skin surface of a healthy patient and is thus visible to the unaided eye. Veins that are not near the surface or which may be difficult to see due to other reasons including age, health, and the condition of the patient's skin are much more challenging to access. One prior art solution is to apply light by fiberoptic or LED technology directly to the skin to transilluminate and therefore highlight otherwise difficult to see veins. The Veinlite® vein finder performs that function.
Visible light-reliant vein finders have less utility finding veins that are not near the surface or which are hard to see for other reasons. Such devices also have a very limited amount of area that can be visualized at one time (typically 31 mm at most).
A device that does not rely upon visible light is sold under the trademark Veinsite® hands-free vascular imaging system; it is worn as head gear and is disclosed in U.S. Pat. No. 7,532,746 which patent is hereby incorporated by reference into this disclosure. Near-infrared radiation is aimed at a patient's limb from emitters located in the Veinsite® headgear and an integrated infrared sensitive video camera images the same area. The computer and optically processed video camera image is displayed on a grayscale LCD screen positioned in front of the user's eyes. Hemoglobin contained in the blood vessels absorbs the near-infrared light while other tissues scatter the radiation. The contrast between absorption and scattering is displayed on the LCD screen, thereby allowing the user to perceive the location of underlying vessels that are not easily seen with an unaided eye. With the displayed image, an intravenous catheter or hypodermic needle can be effectively guided to access the vessel. If needed, the user can see the treatment area directly with the unaided eye by directing the eyes downward, i.e., not observing the display screen. This device also allows viewing of large areas of the skin simultaneously.
Other devices that use near-infrared radiation for vein detection and which include a projector are known commercially as the VeinViewer® and the AccuVein® vein viewing system.
The term “near-infrared” as used in this disclosure includes infrared radiation as well for claim interpretation purposes. “Near-infrared” radiation is defined in Wikipedia as having a wavelength in the range of from about 800 nm to 2500 nm and “infrared radiation” is defined by Wikipedia as having a wavelength from about 700 nm to 1 mm (one millimeter being one million nanometers). Visible light is defined as having a wavelength from about 390 nm to 700 nm. The infrared range of 700 nm to 1,000,000 nm clearly includes the near-infrared range of 800 nm to 2500 nm.
Although these devices perform well, the only training they provide is on-the-job training, i.e., the clinician uses the device for the first time on a patient.
Thus there is a need for a training device that in combination with near-infrared vein finders simulates the appearance and relative depths of veins in a way that enables a clinician to practice intravenous access before locating a vein in a patient. Development of psychomotor skills prior to clinical and live patient use provides greater chance of procedural success and serves to lessen patient discomfort.
Prior art vein finding practice devices for visual vein access practice have major drawbacks that do not allow their use with near-infrared devices. First, they are made of materials that do not transmit near-infrared light. Secondly, the liquid fluid material used to simulate blood does not absorb near-infrared light. Another drawback is that simulation of the relative depth of the vessel cannot be achieved.
There is a need for a training device for near-infrared imagers formed of a material that re-seals itself after puncture and subsequent retraction of a needle. The device would have non-toxic blood-simulating liquid fluid in the simulated veins, and said liquid fluid would be visible under near-infrared imaging. Moreover, veins that are close to the surface would be imaged as clear black images and veins further from the surface would be imaged as gray images that appear lighter gray and have less edge definition with increased depth.
However, in view of the art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the art how the needed training device could be provided.